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Ileal Digestibility of Nitrogen and Amino Acids in Human Milk and an Infant Formula as Determined in Neonatal Minipiglets
(Elsevier Inc. on behalf of American Society for Nutrition, 2023-04) Charton E; Henry G; Cahu A; Le Gouar Y; Dahirel P; Moughan PJ; Montoya CA; Bellanger A; Dupont D; Le Huërou-Luron I; Deglaire A
BACKGROUND: Infant formula (IF) has to provide at least the same amount of amino acids (AAs) as human milk (HM). AA digestibility in HM and IF was not studied extensively, with no data available for tryptophan digestibility. OBJECTIVES: The present study aimed to measure the true ileal digestibility (TID) of total nitrogen and AAs in HM and IF to estimate AA bioavailability using Yucatan mini-piglets as an infant model. METHODS: Twenty-four 19-day-old piglets (males and females) received either HM or IF for 6 days or a protein-free diet for 3 days, with cobalt-EDTA as an indigestible marker. Diets were fed hourly over 6 h before euthanasia and digesta collection. Total N, AA, and marker contents in diets and digesta were measured to determine the TID. Unidimensional statistical analyses were conducted. RESULTS: Dietary N content was not different between HM and IF, while true protein was lower in HM (-4 g/L) due to a 7-fold higher non-protein N content in HM. The TID of total N was lower (P < 0.001) for HM (91.3 ± 1.24%) than for IF (98.0 ± 0.810%), while the TID of amino acid nitrogen (AAN) was not different (average of 97.4 ± 0.655%, P = 0.272). HM and IF had similar (P > 0.05) TID for most of the AAs including tryptophan (96.7 ± 0.950%, P = 0.079), except for some AAs (lysine, phenylalanine, threonine, valine, alanine, proline, and serine), with small significant difference (P < 0.05). The first limiting AA was the aromatic AAs, and the digestible indispensable AA score (DIAAS) was higher for HM (DIAASHM = 101) than for IF (DIAASIF = 83). CONCLUSION: HM, compared to IF, had a lower TID for total N only, whereas the TID of AAN and most AAs, including Trp, was high and similar. A larger proportion of non-protein N is transferred to the microbiota with HM, which is of physiological relevance, although this fraction is poorly considered for IF manufacturing.
Review and update of a Nutrient Transfer model used for estimating nitrous oxide emissions from complex grazed landscapes, and implications for nationwide accounting
(John Wiley and Sons Inc on behalf of American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, 2022-09-30) Vibart R; Giltrap D; Saggar S; Mackay A; Betteridge K; Costall D; Rollo M; Draganova I; Zhu-Barker. X
In New Zealand, nitrous oxide emissions from grazed hill pastures are estimated using different emission factors for urine and dung deposited on different slope classes. Allocation of urine and dung to each slope class needs to consider the distribution of slope classes within a landscape and animal behavior. The Nutrient Transfer (NT) model has recently been incorporated into the New Zealand Agricultural GHG Inventory Model to account for the allocation of excretal nitrogen (N) to each slope class. In this study, the predictive ability of the transfer function within the NT model was explored using urine deposition datasets collected with urine sensor and GPS tracker technology. Data were collected from three paddocks that had areas in low (<12°), medium (12-24°), and high slopes (>24°). The NT model showed a good overall predictive ability for two of the three datasets. However, if the urine emission factors (% of urine N emitted as N2 O-N) were to be further disaggregated to assess emissions from all three slope classes or slope gradients, more precise data would be required to accurately represent the range of landscapes found on farms. We have identified the need for more geospatial data on urine deposition and animal location for farms that are topographically out of the range used to develop the model. These new datasets would provide livestock urine deposition on a more continuous basis across slopes (as opposed to broad ranges), a unique opportunity to improve the performance of the NT model.
Transcriptomic Identification of a Unique Set of Nodule-Specific Cysteine-Rich Peptides Expressed in the Nitrogen-Fixing Root Nodule of Astragalus sinicus
(The American Phytopathological Society in cooperation with the International Society for Molecular Plant-Microbe Interactions, 2022-10-08) Wei F; Liu Y; Zhou D; Zhao W; Chen Z; Chen D; Li Y; Zhang X-X
Legumes in the inverted repeat-lacking clade (IRLC) each produce a unique set of nodule-specific cysteine-rich (NCR) peptides, which act in concert to determine the terminal differentiation of nitrogen-fixing bacteroid. IRLC legumes differ greatly in their numbers of NCR and sequence diversity. This raises the significant question how bacteroid differentiation is collectively controlled by the specific NCR repertoire of an IRLC legume. Astragalus sinicus is an IRLC legume that forms indeterminate nodules with its microsymbiont Mesorhizobium huakuii 7653R. Here, we performed transcriptome analysis of root and nodule samples at 3, 7, 14, 28 days postinoculation with M. huakuii 7653R and its isogenic ∆bacA mutant. BacA is a broad-specificity peptide transporter required for the host-derived NCRs to target rhizobial cells. A total of 167 NCRs were identified in the RNA transcripts. Comparative sequence and electrochemical analysis revealed that A. sinicus NCRs (AsNCRs) are dominated by a unique cationic group (termed subgroup C), whose mature portion is relatively long (>60 amino acids) and phylogenetically distinct and possessing six highly conserved cysteine residues. Subsequent functional characterization showed that a 7653R variant harboring AsNCR083 (a representative of subgroup C AsNCR) displayed significant growth inhibition in laboratory media and formed ineffective white nodules on A. sinicus with irregular symbiosomes. Finally, bacterial two-hybrid analysis led to the identification of GroEL1 and GroEL3 as the molecular targets of AsNCR067 and AsNCR076. Together, our data contribute to a systematic understanding of the NCR repertoire associated with the A. sinicus and M. huakuii symbiosis.
Role of a local transcription factor in governing cellular carbon/nitrogen homeostasis in Pseudomonas fluorescens
(Oxford University Press on behalf of Nucleic Acids Research, 2021-04-06) Naren N; Zhang X-X
Autoactivation of two-component systems (TCSs) can increase the sensitivity to signals but inherently cause a delayed response. Here, we describe a unique negative feedback mechanism enabling the global NtrB/NtrC regulator to rapidly respond to nitrogen starvation over the course of histidine utilization (hut) in Pseudomonas fluorescens. NtrBC directly activates transcription of hut genes, but overexpression will produce excess ammonium leading to NtrBC inactivation. To prevent this from occurring, the histidine-responsive repressor HutC fine-tunes ntrBC autoactivation: HutC and NtrC bind to the same operator site in the ntrBC promoter. This newly discovered low-affinity binding site shows little sequence similarity with the consensus sequence that HutC recognizes for substrate-specific induction of hut operons. A combination of genetic and transcriptomic analysis indicated that both ntrBC and hut promoter activities cannot be stably maintained in the ΔhutC background when histidine fluctuates at high concentrations. Moreover, the global carbon regulator CbrA/CbrB is involved in directly activating hut transcription while de-repressing hut translation via the CbrAB-CrcYZ-Crc/Hfq regulatory cascade. Together, our data reveal that the local transcription factor HutC plays a crucial role in governing NtrBC to maintain carbon/nitrogen homeostasis through the complex interactions between two TCSs (NtrBC and CbrAB) at the hut promoter.
Nutrient criteria to achieve New Zealand's riverine macroinvertebrate targets
(PeerJ, Inc, 2021) Canning AD; Joy MK; Death RG; Brauns M
Waterways worldwide are experiencing nutrient enrichment from population growth and intensive agriculture, and New Zealand is part of this global trend. Increasing fertilizer in New Zealand and intensive agriculture have driven substantial water quality declines over recent decades. A recent national directive has set environmental managers a range of riverine ecological targets, including three macroinvertebrate indicators, and requires nutrient criteria be set to support their achievement. To support these national aspirations, we use the minimization-of-mismatch analysis to derive potential nutrient criteria. Given that nutrient and macroinvertebrate monitoring often does not occur at the same sites, we compared nutrient criteria derived at sites where macroinvertebrates and nutrients are monitored concurrently with nutrient criteria derived at all macroinvertebrate monitoring sites and using modelled nutrients. To support all three macroinvertebrate targets, we suggest that suitable nutrient criteria would set median dissolved inorganic nitrogen concentrations at ~0.6 mg/L and median dissolved reactive phosphorus concentrations at ~0.02 mg/L. We recognize that deriving site-specific nutrient criteria requires the balancing of multiple values and consideration of multiple targets, and anticipate that criteria derived here will help and support these environmental goals.
Drought stress responses of the Medicago truncatula - Ensifer meliloti symbiosis on nodule senescence and nitrogen fixation : a thesis presented in fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Science at Massey University, Palmerston North, New Zealand
(Massey University, 2018) Dhanushkodi, Ramadoss
While the use of nitrogen (N) fertilizer has provided many benefits to agriculture, incessant use of it can reduce soil organic matter and fertility resulting in lower crop yields. Legume plants can fix its own N2 through symbiotic nitrogen fixation (SNF) to promote plant growth by developing facultative root organs called nodules. Therefore, increasing the rate of SNF to reduce dependence on N fertilizer is a promising strategy for sustainable legume production. In legume cultivation this symbiotic process confronts two major challenges. First, SNF is suppressed by readily available N in the soil and second, the early senescence of N-fixing nodules can limit any further fixation to occur. Previous reports show that N fertilizer supresses SNF activity in many legumes and supports plant growth better than SNF. Moreover, suppression of SNF can also be induced by drought stress which causes early nodule senescence and subsequent reduced rates of plant growth. This thesis addresses the process of SNF suppression in two Medicago truncatula selected genotypes in response to external N treatment and also delivers a molecular view on the regulation of drought-induced nodule senescence processes.--Shortened abstract
The influence of cultural practices on soil organic matter, soil biomass size and nitrogen leaching : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science (Agricultural Environmental Science) at Massey University, New Zealand
(Massey University, 1994) Mapfumo, Phillimon
The effects of bare fallow, cultivation and nitrogen application on soil organic matter, soil biomass and nitrogen leaching were compared against the backgrounds of permanent grass pasture and grass/clover pasture. Cultivated plots were dug annually to a depth of 15cm. All plots received an annual dressing of 300kg ha·1 of Potassic Super. The Nitrogen treatment was applied as two equal applications of 100kg ha·1 Calcium Ammonium Nitrate in November and December each year. The results indicated that both bare fallowing and cultivation reduced soil organic matter and soil microbial biomass. The use of N-fertilizer did not promote either the soil organic matter or soil microbial biomass; this is contrary to the general finding. Legume nitrogen was found to leach as readily as the applied nitrogen and hence posed an environmental threat to groundwater quality. In all cultural practices the largest concentration of nitrate nitrogen (NO3-N) was observed at the 50 - 100m depth, below the root zone. Vertical movement of groundwater was estimated at lm year·1 This confirmed the concern of possible groundwater pollution by nitrate nitrogen from agricultural activities.
Effect of nitrogen fertilizer placement on nitrogen uptake and yield of sweet corn (Zea mays L. saccharata) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Plant Science at Massey University, New Zealand
(Massey University, 1986) Wongpichet, Kitti
Five placements of nitrogen fertilizer applied to sweet corn (Zea mays L. saccharata) at the four fully expanded leaf stage, that is control (no nitrogen), a band of nitrogen placed on the soil surface near the row, on the soil surface between the rows, at 3 cm depth between the rows and at 10 cm depth between the rows were studied following three sowing times. Total plant nitrogen and sap nitrate were determined along with total plant dry weight at six growth stages. Leaf extension and leaf appearance were also followed in order to monitor the response of plants to nitrogen fertilizer applied. Nitrogen fertilizer application resulted in significantly higher nitrogen uptake, plant dry weight and marketable ears under both dry and wet conditions. Nitrogen fertilizer applied at 10 cm depth between rows resulted in significantly higher nitrogen uptake, plant dry weight and marketable ears than that applied on the soil surface between rows under dry condition. Nitrogen fertilizer applied on the soil surface near the plants performed well under both dry and wet conditions. The sap nitrate test was more sensitive than total nitrogen measurement in indicating the timing of nitrogen uptake. Sap nitrate levels were influenced by nitrogen fertilizer application and soil water content. The general critical value of sap nitrate over the vegetative growing period was about 1000 ppm. The sap nitrate test appeared to be a very useful monitoring tool for plant nitrogen status. Further studies in the uses of sap nitrate test, especially the critical value, are needed. Use of leaf extension to detect the response of plants to nitrogen fertilizer applied was not successful. Nitrogen fertilizer application tended to accelerate leaf appearance under the low soil nitrogen status.
Sources and transport of phosphorus and nitrogen in a stream draining a dominantly pasture catchment : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science at Massey University
(Massey University, 1977) Sharpley, Andrew Neville
The literature relating to the sources and amounts of P and N forms transported in runoff types (surface, accelerated subsurface, and subsurface runoff) and in stream flow from catchments of varying land use was reviewed. There is a paucity of information available on this topic for New Zealand situations. Concentration-flow relationships of P and N forms varied between different runoff types in the dominantly pasture catchment under study. Flow was the more important variable, however, in determining the P and N loadings in each runoff type. Because of more rapid fluctuations in P and N concentrations, surface and accelerated subsurface runoff, and storm flow in the stream, smaller sampling intervals were required than for subsurface runoff in order to obtain reliable estimates of P and N loadings. An appreciably greater proportion of fertilizer P was transported in surface runoff from 13 and 6° undrained slopes (6.7 and 5.6% as TP, respectively) than from a 6° drained slope (1.0%) in four months following application (50kgP ha-1). This could be attributed to a four-fold reduction in the volume of surface runoff from drained slopes. Although 0.77 and 4.18kg ha-1 of total P (TP) and total N (TN), respectively, were transported in surface runoff in four weeks as a result of grazing with dairy cattle, the effect of grazing was less sustained than that due to fertilizer P application. Following the application of urea to the drained area of a 20-ha subcatchment, 2.3% of the applied N was lost as TN (87% as NO3) in tile drainage in a four-week period. Although the volume of tile drainage was dramatically reduced following grazing, the concentrations of P and N forms increased. The effect of grazing on N concentrations in tile drainage was not as sustained as that of urea application. Highly significant correlations were obtained between extractable soil P in surface soil (0-10cm) and the dissolved inorganic P (DIP) concentrations in surface runoff, and between extractable soil P and nitrate (NO3) in the subsoil (40-50cm) and the DIP and NO3 loadings, respectively, of tile drainage. A much greater amount of N (13.15 and l6.32kg ha-1 y-1 as NO3 and TN, respectively) than of P (0.43 and 1.31kg ha-1 y-1 as total dissolved P (TDP) and TP, respectively) was transported in stream flow in 1975. Although surface runoff contributed the major proportion of P transported (18% for TP) by the runoff types, streambank erosion contributed 64 and 67%, respectively, of the TP and sediment transported in stream flow during 1975. The major proportion of stream flow (67%) and N transported (59% as TN), however, was contributed by subsurface runoff. Earthworm casts contained appreciably more inorganic P (IP) than underlying soil, of which 90% of the additional IP was held by a more-physical sorption type and thus, readily released to solution. The data point to the importance of surface casts as a potential source of particulate material and P in surface runoff, and in the cycling of P in a soil under pasture. A differing ability of potential source and suspended-particulate materials to sorb and release IP from solution was observed and this was related, with some success, to field data.
Protein metabolism in the adult domestic cat (Felis catus) : a thesis presented in partial fulfilment of the requirement for the degree of Doctor of Philosophy (Animal Science) at Massey University, Palmerston North, New Zealand
(Massey University, 1996) Hendriks, Wouter H.; Hendriks, Wouter H.
The main objective of this study was to provide information for the determination of the protein and amino acid requirements of the adult domestic cat by the factorial method. Data are presented on four factors for a factorial model: (1) the endogenous amino acids excreted in the faeces, (2) the amino acids which are required for the replacement of hair, (3) the body amino acids which are catabolised and ultimately voided in the urine and (4) the excretion of the urinary amino acid felinine. Endogenous ileal nitrogen and amino acid excretions were determined under the conditions of protein-free and peptide (enzymatically hydrolysed casein, molecular weight < 10,000 Da) alimentation while the relative contribution of the hindgut to total endogenous gut excretion was investigated in a separate study by feeding cats a protein-free diet with or without added antibiotics. Endogenous ileal nitrogen and amino acid nitrogen excretions (mean ± SEM) of 2.4 ± 0.27 and 1.9 ± 0.13 mg/g food dry matter intake, respectively, were found for the cats fed the protein-free diet, whereas higher excretions of 3.6 ± 0.73 (P = 0.12) and 3.6 ± 0.76 (P = 0.03) mg/g food dry matter intake were obtained under the condition of peptide alimentation. Significantly (P < 0.05) higher endogenous ileal amino acid excretions, for the enzymatically hydrolysed casein-fed cats compared with those fed the protein-free diet, were found for methionine, aspartic acid, serine, glutamic acid, proline, valine and isoleucine, with the differences in excretions of glycine, alanine, leucine and histidine being significant at the 6 % level. Most of the endogenous faecal amino acid excretions were unaffected by the inclusion of the antibiotics in the protein-free diet, although bacterial numbers were significantly (P < 0.01) reduced (69 %). Antibiotics addition led to significantly higher faecal endogenous excretions of nitrogen, taurine, threonine, serine and histidine but significantly lower excretions for methionine and lysine. Nitrogen and amino acids required for the growth of hair were estimated by the measurement of hair growth and loss rates for adult male and female domestic short-haired cats, and the nitrogen and amino acid composition of cat hair. Hair growth rate was determined using the mid-side patch technique in combination with the ratio of hair on the mid-side area to total hair on the body to allow conversion of mid-side hair growth rates to hair growth rates over the entire body. Hair loss rate was determined in a separate experiment by quantitative collection of ingested and non-ingested hair loss. The mid-side hair growth and the hair loss rates showed a sinusoidal pattern throughout the year. The peak hair growth rate for the female cats was reached earlier than that for the male cats. Hair loss rate was 75 d out of phase with hair growth rate. The estimate for the total amount of hair growth throughout the year (32.7 g.kg-1body weight) was similar to the estimate for the total amount of hair loss throughout the year (28.1 g.kg-1body weight). The amino acid composition of cat hair was determined by conventional 24 h acid hydrolysis and by a compartmental model which took into account the simultaneously occurring processes of hydrolysis and degradation of amino acids over time. Four colours of cat hair, were also analysed (24 h hydrolysis) to determine if there was an effect of hair colour on amino acid composition. There was no significant (P > 0.05) effect of hair colour on the amino acid composition of cat hair. Amino acid nitrogen accounted for 94 and 99 % of the total nitrogen when determined by conventional 24 h hydrolysis and the compartmental model, respectively. The accurate amino acid composition of cat hair is presented. Endogenous urinary excretions of total, urea, ammonia and creatinine nitrogen in the adult cat were determined by feeding cats a protein-free diet or by regression to zero protein intake of urinary nitrogen metabolite excretions for adult cats fed four levels of dietary protein. The mean (± SEM) endogenous total, urea and ammonia nitrogen excretions for the cats fed the protein-free diet were 360 (± 11.3), 243 (± 8.8) and 27.6 (± 1.06) mg·kg-0.75 body weight·d-1, respectively. Lower mean (± SEM) estimates of 316 (± 53.9) and 232 (± 43.4) mg·kg-0.75 body weight·d-1 were obtained for the endogenous excretions of total and urea nitrogen, respectively using the regression technique while a higher endogenous urinary ammonia nitrogen excretion of 33.7 (± 5.68) mg·kg-0.75 body weight·d-1 was found. The differences between the two techniques were not statistically significant. Daily excretions of creatinine nitrogen were not significantly (P = 0.64) different (mean ± SEM, 16.2 ± 0.46 and 17.5 ± 1.19 mg·kg-0.67 body weight, respectively) for the two methods. The chemical body composition of male and female adult cats was determined to obtain an estimate of the pattern of endogenous amino acid catabolism. Dehaired empty cat bodies were subjected to analysis for dry matter, lipid, ash, crude protein, amino acids, and several minerals (Ca, P, K, Mg, Fe, Mn and Zn). The chemical body composition was found to be similar between male and female cats except for the amount of crude protein which was significantly (P < 0.05) higher on a wet tissue (21.7 ± 0.35 % vs. 20.0 ± 0.60 %), lipid-free matter (24.1 ± 0.22 % vs. 23.0 ± 0.22 %) and lipid-free dry matter (80.7 ± 0.23 % vs. 78.3 ± 0.32 %) basis in the male cats compared to the female cats. There was no significant (P > 0.05) effect of gender on the whole body amino acid composition (lipid-free dry matter or mol % basis) except for cysteine which was significantly (P < 0.05) lower in the male cats in comparison to the female cats. A review on the urinary amino acid, felinine, which can be found in cat urine is presented. The biological significance of felinine to the animal is still a matter for speculation, but its function as a precursor to a pheromone seems likely. To obtain a standard for quantification experiments, several published synthesis procedures reported leading to (±)-felinine were evaluated for their yield. Most of the procedures were found to produce an amino acid isomeric with felinine. The yield for the only evaluated synthesis procedure shown to produce felinine was found to be low. A new higher yielding method for the synthesis of (±)-felinine is presented. In a separate study, normal urinary excretions of felinine by entire male, castrated male, entire female and spayed female cats were determined and were found to be (mean ± SEM) 122 ± 23.6, 41 ± 8.4, 36 ± 7.3 and 20 ± 3.8 µmol·kg-1 body weight·d-1, respectively.

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